Ink jet head method of production thereof, and jig for producing ink jet head

ABSTRACT

The present invention relates to an ink jet head for changing the volume in a pressure chamber by deformation of a laminate piezoelectric device and for jetting ink filled in the pressure chamber from the front openings of the pressure chamber through nozzle holes, and particularly to an ink jet head which is characterized by an adhesive layer interposed between the front end surface of the main body forming the pressure chamber and a nozzle plate. The nozzle plate is bonded to the front end surface of the main body via an adhesive layer formed by an adhesive. The adhesive layer is divided into a nozzle seal layer encompassing the nozzle holes and the periphery of the front openings of the pressure chamber, an outer periphery hermetic layer formed annularly around the outer periphery of a region in which the main body and the nozzle plate oppose each other, and a reinforcing layer distributed in an intermediate portion between the nozzle seal layer and the outer periphery hermetic layer.

This application is a PCT/JP96/01588 filed Jun. 12, 1996.

TECHNICAL FIELD

The present invention relates to an ink jet head for changing the volumein a pressure chamber by deformation of a laminate piezoelectric deviceand for jetting ink filled in the pressure chamber from the frontopenings of the pressure chamber through nozzle holes, particularly toan ink jet head which is characterized by an adhesive layer interposedbetween the front end surface of the main body forming the pressurechamber and a nozzle plate, a method of manufacturing the same, and ajig for manufacturing the ink jet head.

BACKGROUND TECHNOLOGY

A conventional ink jet head of this type is, for example, disclosed inthe laid-open publication of JP-A 3-173651.

FIG. 8 shows the entire structure of the ink jet head as disclosed inthe same publication, wherein a nozzle forming member 102 is bonded to apiezoelectric converter 101 fixedly secured onto a base member 100 by anadhesive 103.

The base member 100, the piezoelectric converter 101 and the nozzleforming member 102 are respectively incorporated in a frame 104, whereinan ink chamber 105 is formed in an intermediate portion between thepiezoelectric converter 101 and the nozzle forming member 102. Ink 106filled in the ink chamber 105 is discharged from nozzle holes 107 bydeformation of the piezoelectric converter 101.

FIG. 9 is an enlarged sectional view showing in detail a construction ofa bonding part between the piezoelectric converter 101 and the nozzleforming member 102 and the periphery thereof shown in FIG. 8. Thepiezoelectric converter 101 and the nozzle forming member 102 are bondedto each other by the adhesive 103 including space restriction particles110 and conductive particles 111. Each of the space restrictionparticles 110 has a uniform grain size. A given gap, namely, the inkchamber 105, is formed between the piezoelectric converter 101 and thenozzle forming member 102 by the space restriction particles 110.

Meanwhile, the ink jet head as disclosed in the publication of JP-A3-173651 has a structure that the end part of the nozzle forming member102 is bonded to the piezoelectric converter 101, and the ink chamber105 having a given interval is formed between the piezoelectricconverter 101 and the nozzle forming member 102 as is evident from FIG.9.

If the bonding spot of the nozzle forming member 102 is limited to theend part alone as set forth above, it is not necessary to consider anyharmful effect like the nozzle holes 107 being blocked owing to theexpansion of the adhesive 103. Accordingly, there is no description inpublication JP-A 3-173651 regarding the amount of coating of theadhesive 103.

However, the amount of coating of the adhesive becomes a problem, forexample, in the case where an entire back surface of a nozzle plate 201is bonded to an end surface 200 a of a piezoelectric module 200 in theink jet head shown in FIG. 10.

That is, if the adhesive is coated onto the entire surfaces between thebonding surfaces of the end surface 200 a of the piezoelectric module200 and the nozzle plate 201, excess adhesive inevitably expands to theperiphery thereof. Particularly, when the adhesive enters gaps 202forming the ink chamber, there is a likelihood that the dischargecharacteristic of the ink will be deteriorated or nozzle holes 203 willbe blocked.

The laid-open publication of JP-A 5-220966 discloses a method ofpreventing the ink chamber and the nozzle holes from being blocked bythe expansion of the excess adhesive set forth below.

That is, a method of manufacturing the ink jet head disclosed in thesame publication comprises supplying an adhesive 302 to a recessed plate300 having a recessed part 301 as shown in FIG. 11A, then scraping offthe excess adhesive 302 which bulges onto the recessed plate 300 by ablade 303 as shown in FIG. 11B, thereby leaving the adhesive 302 in therecessed part 301 alone.

Successively, the end surface (bonding surface of the nozzle plate) 200a of the piezoelectric module 200 is pressed against the recessed part301, and then the piezoelectric module 200 is extracted thereafter sothat a small amount of adhesive 302 is uniformly coated onto the endsurface 200 a of the piezoelectric module 200, as shown in FIG. 11C.

In such a manner, the method prevents the expansion of the excessadhesive 302 by bonding the nozzle plate 201 to the end surface 200 a ofthe piezoelectric module 200 onto which the adhesive 302 is coated.

However, even in the method of manufacturing the ink jet head disclosedin the above-mentioned publication, there is a high possibility that theadhesive 302 filled in the bonding surfaces contains bubbles at randomsince the adhesive 302 is coated onto the entire bonding surfaces of thepiezoelectric module 200 and the nozzle plate 201.

If the adhesive 302 hardens while it contains bubbles, hermeticitybetween the piezoelectric module 200 and the nozzle plate 201 is notmaintained depending on the condition or position of the bubbles,thereby leading to a danger that ink leakage will occur and an electrodeof the piezoelectric module 200 will be short-circuited.

The present invention has been made in view of these circumstances, andit is an object of the invention to bond between the front end surfaceof the main body and the nozzle plate strongly with high hermeticity,and to prevent the nozzle holes from being blocked by the expansion ofthe adhesive.

DISCLOSURE OF THE INVENTION

To achieve the above object, the ink jet head of the present inventionis characterized in being structured as follows.

That is, the ink jet head comprises a main body for changing the volumein a pressure chamber by deformation of a laminate piezoelectric device,and feeding ink filled in the pressure chamber toward front openings ofthe pressure chamber, a nozzle plate having nozzle holes communicatingwith the front openings of the pressure chamber, and an adhesive layerformed between the front end surface of the main body and the nozzleplate by an adhesive.

The adhesive layer formed between the main body of the ink jet head andthe nozzle plate comprises a nozzle seal layer of an arbitrary width insuch a manner as to encompass the nozzle holes and the periphery of thefront openings of the pressure chamber, an outer periphery hermeticlayer of an arbitrary width being formed annularly around the outerperiphery of a region in which the main body and the nozzle plate opposeeach other, and a reinforcing layer being distributed in an intermediateportion between the nozzle seal layer and the outer periphery hermeticlayer.

Since the nozzle holes and the front openings of the pressure chamberare sealed by the nozzle seal layer in the present invention having theconstruction set forth above, it is possible to prevent ink from leakingfrom the nozzle holes and the front openings.

Further, a sealing property can be further enhanced by the outerperiphery hermetic layer, and particularly entrance of moisture, dust,etc., from the outside can be prevented. Still further, a large bondingstrength can be secured by the reinforcing layer.

Further, a plurality of spherical bodies each having an extremely smalldiameter may be contained in the adhesive layer according to the ink jethead of the present invention. With such a construction, the thicknessof the adhesive layer can be maintained constant by the existence of thespherical bodies, and the nozzle seal layer, the outer peripheryhermetic layer and the reinforcing layer can be prevented from beingcollapsed so as to effectively perform their functions.

Meanwhile, a method of manufacturing an ink jet head of the presentinvention, comprising a main body for changing the volume in a pressurechamber by deformation of a laminate piezoelectric device, and feedingink filled in the pressure chamber toward the front openings of thepressure chamber, and a nozzle plate bonded onto the front end surfaceof the main body in a state where nozzle holes communicate with thefront openings of the pressure chamber, is characterized in comprisingthe following steps.

Adhesive coating step

In this step, the adhesive is coated onto the nozzle plate in such amanner as to encompass the front openings at the front end surface ofthe main body with an arbitrary width. Further, the adhesive is coatedannularly along an outer periphery edge with an arbitrary width in aregion where the nozzle plate is bonded to the front end surface of themain body. Still further, the adhesive is coated onto an intermediateregion which is encompassed by each portion onto which the adhesive iscoated in a distributed manner.

Since the adhesive is coated in such a manner, the nozzle seal layer,the outer periphery hermetic layer, and the reinforcing layer in the inkjet head of the present invention can be formed as mentioned in theforegoing.

Overlaying step

In this step, the nozzle plate is overlaid on the front end surface ofthe main body in a state where the nozzle holes conform to the frontopenings of the pressure chamber.

Pressing step

In this step, the nozzle plate which is overlaid on the front endsurface of the main body in the overlaying step is pressed elastically.Since the nozzle plate is pressed elastically, the pressure applied tothe adhesive is appropriately lessened to prevent the adhesive frombeing collapsed.

If a plurality of spherical bodies each having an extremely smalldiameter are contained in the adhesive used in the adhesive coatingstep, the thickness of the adhesive layer can be maintained constant bythe existence of the spherical bodies so as to prevent the adhesive frombeing collapsed.

Each step of the method of manufacturing the ink jet head of the presentinvention may be carried out in the following method.

Adhesive coating step

The adhesive is coated onto the nozzle plate in such a manner as toencompass the nozzle holes with an arbitrary width. Further, theadhesive is coated annularly along an outer periphery edge with anarbitrary width in a region where the nozzle plate is bonded to thefront end surface of the main body. Still further, the adhesive iscoated onto an intermediate region which is encompassed by each portiononto which the adhesive is coated in a distributed manner.

Overlaying step

The front end surface of the main body is overlaid on the nozzle platein a state where the front openings of the pressure chamber conform tothe nozzle holes.

Pressing step

The nozzle plate overlaid on the front end surface of the main body iselastically pressed.

Also in this case, if plural spherical bodies each having an extremelysmall diameter are contained in the adhesive used in the adhesivecoating step, the thickness of the adhesive layer can be maintainedconstant by the existence of the spherical bodies so as to prevent theadhesive from being collapsed.

Still further, the present invention provides a jig adapted for carryingout the method of manufacturing the ink jet head set forth above.

That is, the jig for manufacturing an ink jet head of the presentinvention comprises a main body of the jig for supporting the main bodyof the ink jet head, a pressing plate for supporting the nozzle platewhile opposing the main body of the ink jet head supported by the mainbody of the jig, the pressing plate being freely movable in a directionof the main body of the jig, an elastic member provided on the pressingplate for elastically supporting the nozzle plate, and a suction meansprovided on the pressing plate for suctioning the nozzle plate againstthe elastic member.

Since the nozzle plate is pressed elastically by the elastic member inthe jig for manufacturing the ink jet head, the pressing step in themethod of manufacturing the ink jet head set forth above can be easilyperformed, and also the pressure applied to the adhesive isappropriately lessened to prevent the adhesive from being collapsed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of an ink jet head according to a mode forcarrying out the invention in which the ink jet head is partially cutoff.

FIG. 2 is a side sectional view of the ink jet head shown in FIG. 1.

FIG. 3 is a front sectional view of the ink jet head shown in FIG. 1.

FIG. 4 is a perspective view showing a laminate piezoelectric deviceunit and a flexible printed-circuit board in the ink jet head shown inFIG. 1.

FIG. 5 is a front view showing a state where an adhesive is coated ontothe front end surface of the main body of the ink jet head shown in FIG.1.

FIG. 6 is a front sectional view showing a jig for manufacturing the inkjet head shown in FIG. 1.

FIG. 7 is a bottom view showing a pressing plate of the jig shown inFIG. 6.

FIG. 8 is a sectional view for explaining the prior art disclosed in thepublication of JP-A 3-173651.

FIG. 9 is an enlarged sectional view for explaining the prior artdisclosed in the publication of JP-A 3-173651, like FIG. 8.

FIG. 10 is a perspective view for explaining another prior art disclosedin the publication of JP-A 5-220966.

FIG. 11A is a sectional view for explaining the prior art disclosed inthe publication of JP-A 5-220966, like FIG. 10.

FIG. 11B is a sectional view continued from FIG. 11A.

FIG. 11C is a sectional view continued from FIG. 11B.

BEST MODE FOR CARRYING OUT THE INVENTION

The best mode for carrying out the present invention will be nowdescribed in detail with reference to the attached drawings.

The overall construction of an ink jet head will be first described withreference to FIGS. 1 to 4.

The ink jet head shown in these figures is provided with a main body 1and a nozzle plate 2 having a plurality of nozzle holes 2 a. The mainbody 1 comprises a pressure chamber 11, a flow path forming member 10forming an ink flow path to the pressure chamber 11, a laminatepiezoelectric device unit 20 which is deformed in the direction of thethickness thereof when a voltage is applied, a diaphragm 30 providedbetween the laminate piezoelectric device unit 20 and the flow pathforming member 10, a flexible printed-circuit board 40 for applying avoltage to the laminate piezoelectric device unit 20, and the like.

The flow path forming member 10 has a common liquid chamber 12 at therear end portion thereof. Ink is supplied to the common liquid chamber12 through an ink supply port 13. A plurality of pressure chambers 11are formed in a line on the bottom surface of the flow path formingmember 10 extending from the intermediate portion to the front endportion thereof. Each pressure chamber 11 communicates with the commonliquid chamber 12 through each orifice 14.

The laminate piezoelectric device unit 20 is bonded to the bottomsurface of the flow path forming member 10 via the diaphragm 30. Thelaminate piezoelectric device unit 20 includes laminate piezoelectricbodies 21 and a base 22. The laminate piezoelectric bodies 21 arestructured in such a manner that a plurality of plate-shapedpiezoelectric members are laminated while they clamp electrode plates 22a and 22 b therebetween as shown in FIG. 2.

Exposed ends of the electrode plates 22 a and 22 b are arrangedalternately to the outside. For example, the electrode plates 22 acorresponding to odd numbers counted from the bottom are exposed fromthe laminate piezoelectric bodies 21 at the rear end thereof, and theelectrode plates 22 b corresponding to even numbers counted from thebottom are exposed from the laminate piezoelectric bodies 21 at thefront end portion thereof.

The laminate piezoelectric bodies 21 are bonded onto the upper surfaceof the base 22, and they are divided into a plurality of piezoelectricdevices 21 a by grooves 23. Each of the piezoelectric devices 21 a(excluding piezoelectric devices 21 b provided at both ends) is providedso as to oppose the pressure chamber 11 via the diaphragm 30.

The piezoelectric devices 21 b provided on both ends of the laminatepiezoelectric bodies 21 serve as a non-driving portion to which novoltage is applied, and serve as supporters for supporting thepiezoelectric devices 21 a provided at the intermediate portion.

A driving concentration electrode 24 is formed on the rear end surfaceof each of the piezoelectric devices 21 a opposing the pressure chamber11, and the electrode plates 22 a exposed from the rear end surface ofeach of the piezoelectric devices 21 a is electrically connected to thedriving concentration electrode 24. Meanwhile, a common concentrationelectrode 25 is formed on the front end surface of each of thepiezoelectric devices 21 a, and the electrode plates 22 b exposed fromthe front end surface of each of the piezoelectric devices 21 a areelectrically connected to the common concentration electrode 25.

A voltage is applied to the driving concentration electrode 24 and thecommon concentration electrode 25 via the flexible printed-circuit board40 as shown in FIG. 4. A plurality of driving conductive patterns 41 anda common conductive pattern 42 are formed on the flexibleprinted-circuit board 40, and each of the driving conductive patterns 41is connected to the driving concentration electrode 24 individually.Further, the common conductive pattern 42 extends to the front endsurface side of the laminate piezoelectric bodies 21 through one edge ofthe base 22 on the upper surface thereof, and is connected to the commonconcentration electrode 25.

When the voltage is applied between the driving concentration electrode24 and common concentration electrode 25 via the flexibleprinted-circuit board 40, each of the piezoelectric devices 21 aopposing the pressure chamber 11 is deformed in the direction of thethickness thereof. This deformation is transmitted to the diaphragm 30to change the volume in the pressure chamber 11. As a result, ink filledin the pressure chamber 11 is discharged from front openings 11 athrough the nozzle holes 2 a.

A frame 50 is provided on the bottom surface of the flow path formingmember 10 to cover the periphery of the laminate piezoelectric deviceunit 20, and the flow path forming member 10 and the laminatepiezoelectric device unit 20 are supported by the frame 50.

A front end surface 1 a of the main body 1 is formed on the front endsurface of the flow path forming member 10, the front end of thediaphragm 30 and the front end surface of the frame 50 according to themode for carrying out the invention as shown in FIG. 2. The nozzle plate2 is joined onto the front end surface 1 a of the main body 1. The frontopenings 11 a of the pressure chamber 11 are bored in the front endsurface 1 a of the main body 1.

The construction of bonding between the front end surface 1 a of themain body 1 and the nozzle plate 2 will be now described together withthe method of manufacturing the ink jet head (see FIG. 1, FIG. 2 andFIG. 5).

The front end surface 1 a of the main body 1 and the back surface of thenozzle plate 2 are finished to become a flat surface having a uniformsurface roughness by grinding or lapping.

Further, a surface to be coated by the adhesive (the front end surface 1a of the main body 1 in this case) is irradiated with UV rays, and anorganic substance on the front surface forms molecules having a simplestructure due to the high energy of the UV rays, and having a strongoxidation strength due to ozone generated by the UV rays, and isvaporized to be removed, so that water repellency is reduced andwettability improves remarkably. As a result, the adhesive can be coatedin a desired shape with uniform height.

The adhesive to be used is selected arbitrarily considering the materialof the main body 1 and nozzle plate 2. Single-liquid type epoxy adhesivehaving 220±20 poids in viscosity is used herein. The adhesive contains aplurality of hard true spherical bodies each having an extremely smalldiameter. The diameter of each of the hard spherical bodies can be setarbitrarily. It must be considered, however, that the diameter of eachhard spherical body determines the thickness of the bonding layer formedbetween the front end surface 1 a of the main body 1 and the nozzleplate 2. In this mode for carrying out the invention, hard sphericalbodies each having a diameter of 0.005 mm are contained in the adhesive.

The adhesive containing such hard spherical bodies is printed and coatedonto the front end surface 1 a of the main body 1 utilizing a screenprinting method (adhesive coating step).

FIG. 5 shows a printing pattern for the adhesive relative to the frontend surface 1 a of the main body 1. As shown in the same figure, theadhesive is printed and coated onto the front end surface 1 a of themain body 1 while being divided into a nozzle seal layer 61, an outerperiphery hermetic layer 62 and a reinforcing layer 63.

The nozzle seal layer 61 is formed to encompass the periphery of thefront openings 1 a of each pressure chamber 11. The width of the nozzleseal layer 61 can be set arbitrarily. In this mode for carrying out theinvention, the adhesive is printed and coated with a width of 0.06 mmand a height of 0.01 mm, thereby forming the nozzle seal layer 61.

The outer periphery hermetic layer 62 is formed annularly with anarbitrary width along the outer peripheral edge of the region where thefront end surface 1 a of the main body 1 and the nozzle plate 2 opposeeach other. In the mode for carrying out the invention, the adhesive isprinted and coated with a width of 0.2 mm and a height of 0.01 mm,thereby forming the outer periphery hermetic layer 62.

The reinforcing layer 63 is formed in the intermediate portion betweenthe nozzle seal layer 61 and the outer periphery hermetic layer 62 in adistributed manner. In the mode for carrying out the invention, theadhesive is printed and coated in a plurality of circular patterns eachhaving a diameter of 0.2 mm and a height of 0.01 mm, thereby forming thereinforcing layer 63.

The back surface of the nozzle plate 2 is overlaid and bonded onto thefront end surface 1 a of the main body 1 onto which the adhesive isprinted and coated while it is divided into each layer (overlayingstep). At this time, each of the nozzle holes 2 a defined in the nozzleplate 2 is permitted to conform to the front openings 11 a of thepressure chamber 11, thereby positioning the former relative to thelatter.

Thereafter the nozzle plate 2 is pressed relatively against the mainbody 1 so that the adhesive which is printed and coated onto the frontend surface 1 a of the main body 1 is brought into close contact withthe nozzle plate 2 (pressing step). In this pressing step, the nozzleplate 2 is pressed elastically, thereby realizing a uniform bondingstate.

That is, when any foreign matter is stuck to the front end surface 1 aof the main body 1 or the back surface of the nozzle plate 2, stresscaused by the pressing is concentrated on the portion contacting theforeign matter on the back surface of the nozzle plate 2, whereby thereoccurs the likelihood of the deformation of the nozzle plate 2.

Particularly in the mode for carrying out the invention employing theadhesive containing the hard spherical bodies, there occurs distortionin each portion of the nozzle plate 2 causing gaps to be defined whenthe hard spherical bodies are brought into contact with the nozzle plate2, whereby there occurs the likelihood of deterioration of the sealingproperty in the bonding portions.

Such drawbacks can be avoided by pressing the nozzle plate 2 elasticallyas set forth below.

FIG. 6 is a sectional view showing the jig for manufacturing the ink jethead capable of performing the overlaying step and the pressing stepeasily and accurately. Further, FIG. 7 is a bottom view of a pressingplate of the jig for manufacturing the ink jet head.

The jig for manufacturing the ink jet head is provided with a main body70 of the jig for supporting the main body 1 and a pressing plate 80 forsupporting the nozzle plate 2.

A positioning fixed portion 71 for positioning the main body 1 is formedin the main body 70 of the jig. In the mode for carrying out theinvention, the positioning fixed portion 71 for positioning the mainbody 1 is formed by a recessed part having a shape conforming to theshape of the rear end portion of the main body 1, wherein the rear endportion of the main body 1 is engaged with the positioning fixed portion71 while the front end surface 1 a of the main body 1 is directed upwardso that the main body 1 can be automatically positioned and fixed.

Positioning pins 72 protrude from both side edge portions of the mainbody 70 of the jig and positioning holes 81 in which the positioningpins 72 are engaged are defined in both side edge portions of thepressing plate 80. The pressing plate 80 can be slid along thepositioning pins 72 in a state where the positioning holes 81 areengaged with the positioning pins 72 of the main body 70 of the jig.

A plate-shaped elastic member 82 is provided on the bottom surface ofthe pressing plate 80 opposing the positioning fixed portion 71 forpositioning the main body as shown in FIG. 7. The elastic member 82 isformed by printing, for example, a liquid silicon rubber having anadhesive property which is excellent in heat resistance onto the bottomsurface of the pressing plate 80 by a screen printing process, andthereafter heating and curing it, whereby an elastic member having aYoung's modulus of 5 kgf/cm² with a height of 0.012 to 0.02 mm isformed.

Small grooves 83 each forming a vacuum chuck are defined in the elasticmember 82, and vacuum nozzles 84 are bored in the small grooves 83 toform a suctioning means for suctioning the nozzle plate 2. The vacuumnozzles 84 communicate with a vacuum pump (not shown), and the nozzleplate 2 can be suctioned by and fixed to the elastic member 82 byevacuating the interior of the small grooves 83 by the vacuum pump.

Nozzle positioning pins 85 are provided in the pressing plate 80 toprotrude to both side edge portions of the elastic member 82. Thepositioning holes 2 b for engaging with the nozzle positioning pins 85are defined previously in the nozzle plate 2 wherein the nozzle plate 2can be positioned relative to the pressing plate 80 when the positioningholes 2 b are engaged with the nozzle positioning pins 85.

The positioning fixed portion 71 for positioning the main body 1, thepositioning pins 72 respectively formed on the main body 70 of the jig,the positioning holes 81, the nozzle positioning pins 85 provided on thepressing plate 80 and the positioning holes 2 b defined in the nozzleplate 2 are respectively adjusted in advance so that the nozzle holes 2a of the nozzle plate 2 which is positioned and fixed to the pressingplate 80 oppose the front openings 11 a of the pressure chamber 11 inthe main body 1 which is positioned in the positioning fixed portion 71of the main body 70 of the jig.

The overlaying step and the pressing step can be easily performed asfollows using the jig for manufacturing the ink jet head.

First of all, the main body 1 having the front end surface 1 a ontowhich the adhesive is printed and coated is engaged with the positioningfixed portion 71 for positioning the main body 70 of the jig, and thenozzle plate 2 is positioned onto the elastic member 82 of the pressingplate 80 to suction the former to the latter. Thereafter, the pressingplate 80 is engaged with the positioning pins 72 to slide the pressingplate 80 toward the main body 70 of the jig.

After the nozzle plate 2 suctioned by the pressing plate 80 contacts theadhesive which is printed and coated onto the front end surface 1 a ofthe main body 1, a given pressing force is applied so that the nozzleplate 2 is bonded to the front end surface 1 a of the main body 1. Atthis time, since the elastic member 82 is interposed between thepressing plate 80 and the nozzle plate 2, the nozzle plate 2 is pressedelastically. In this state, a heating process is performed for a giventime to cure the adhesive.

The adhesive layer is formed by the adhesive between the front endsurface 1 a of the main body 1 and the nozzle plate 2 which are bondedto each other as set forth above. The adhesive layer comprises thenozzle seal layer 61, the outer periphery hermetic layer 62 and thereinforcing layer 63 as set forth above, and among them, the nozzle seallayer 61 prevents ink discharged from the front openings 11 a of thepressure chamber 11 from leaking between the bonding surfaces. The outerperiphery hermetic layer 62 prevents moisture, dust, etc., from enteringbetween the bonding surfaces from the outside. The reinforcing layer 63sufficiently secures the bonding strength between the main body 1 andthe nozzle plate 2.

As a result of forming the adhesive layer in the required minimumregion, the expansion of adhesive can be restrained, thereby preventingthe harmful effect that the nozzle holes 2 a are blocked owing to theexpansion of the adhesive.

Further, since the hard spherical bodies are contained in the adhesivein the mode for carrying out the invention, they act as supports whenthe nozzle plate 2 is pressed and brought into contact with the mainbody 1, thereby preventing the adhesive layer from being collapsed. As aresult, the expansion of the adhesive can be further restrained, therebyforming an adhesive having a uniform thickness, so that the bondingstrength is stabilized.

Although the adhesive is coated onto the front end surface 1 a of themain body 1 in the mode for carrying out the invention set forth above,the adhesive may be coated onto the back surface of the nozzle plate 2to overlay on the main body 1.

Further, as the feature of the present invention resides in the bondingportion between the main body and the nozzle plate, the other componentsmay be appropriately changed in design.

INDUSTRIAL APPLICABILITY

The present invention has an effect in the improvement of accuracy ofthe ink jet head employed by an ink jet printer, particularly, in thebonding between the main body and the nozzle plate in appropriatestates, thereby lowering the defective fraction of manufactured ink jetheads remarkably.

What is claimed is:
 1. An ink jet head comprising a main body forchanging the volume in a pressure chamber by deformation of a laminatepiezoelectric device, and feeding ink filled in the pressure chambertoward front openings of the pressure chamber, a nozzle plate havingnozzle holes communicating with the front openings of the pressurechamber, and an adhesive layer formed between the front end surface ofthe main body and the nozzle plate by an adhesive, said adhesive layerformed between the main body and the nozzle plate comprises a nozzleseal layer circumscribing the nozzle holes and the periphery of thefront openings of the pressure chamber to prevent ink leakage betweenthe nozzle plate and the main body, an outer periphery hermetic layerformed annularly around the outer periphery of a region in which themain body and the nozzle plate oppose each other to prevent moistureentering between the nozzle plate and the main body, and a reinforcinglayer being distributed in an intermediate portion between the nozzleseal layer and the outer periphery hermetic layer to secure the bondstrength.
 2. The ink jet head according to claim 1, wherein the adhesivelayer contains a plurality of spherical bodies.